There occurs in industry the need to quickly and efficiently hydrolyze residual amounts of phosphorus trichloride contained in reactors, storage tanks and shipping containers such as tank cars, etc. In one such instance, the reactors employed to produce phosphorus trichloride by the reaction of chlorine and elemental phosphorus must be periodically cleaned out because they accumulate foreign material. After carefully completing the reaction so as to consume the available elemental phosphorus, the reactor is usually opened and water is introduced to hydrolyze the remaining phosphorus trichloride that cannot be removed from the reactor. The usual practice is to carefully flush the reactor or tank with water thereby hydrolyzing the residual phosphorus trichloride to phosphorous acid. It is well known that fires and explosions have occurred while conducting such operations because of the inadvertent formation of highly reactive compounds other than the intended phosphorous acid. Furthermore, vapors may form in the runaway reaction resulting in overloading the scrubber system and allowing pollutants to be emitted into the air.
In studies of the hydrolysis reaction whereby water is added to phosphorus trichloride, it has been noted that the reaction is highly exothermic and that the heat generated by the reaction increases the rate of reaction for the remaining amount of available water. Water droplets have been observed to remain cohesive in a body of phosphorus trichloride until the exothermic reaction heated the local area of the droplet allowing a greatly increased reaction rate thereby further increasing the temperature of the phosphorus trichloride. Because there is some delay in achieving total reaction of the added water in the phosphorus trichloride, excess water may have been added before it is realized that a runaway reaction will occur. As the temperature of the hydrolysis reaction increases it has been found that more highly reactive species such as the lower oxides of phosphorus, phosphines and diphosphines are formed which induce uncontrollable reactions with available water giving rise to the possibility of fire or explosion.
There is therefore needed a safe yet efficient means to economically flush residual phosphorus trichloride from vessels such as storage tanks, shipping containers and particularly reactors which must be regularly cleansed of foreign matter.